Atlas Copco Unloader Valve Kit Replacement – 2906056300

Atlas Copco 2906056300 – Unloader Valve Kit

The Atlas Copco 2906056300 (2906-0563-00) is an Unloader Valve Kit used in the unloading and capacity-control system of compatible Atlas Copco GA-series oil-injected screw compressors.

The unloader valve controls the compressor’s operating condition by regulating the inlet system during loading and unloading. It works together with the compressor’s control circuit to reduce or stop the intake of atmospheric air when the required system pressure has been reached.

Working Process:

During loaded operation, the compressor requires atmospheric air to enter the compression element.

The compressor control system keeps the inlet system in the appropriate operating position, allowing air to enter the compressor element.

The air is compressed and delivered to the compressed-air network.

As system pressure approaches the programmed maximum pressure, the compressor controller initiates the unloading sequence.

The unloader valve is actuated by the compressor control system. It changes the position of the inlet/unloading mechanism and reduces the amount of air entering the compression element.

With the compressor unloaded, the compression element receives little or no effective inlet airflow. This reduces compressor output and prevents the compressor from continuing to produce compressed air when it is not required.

The compressor may then operate in an unloaded condition while the system pressure remains within the required range.

When compressed-air consumption causes the system pressure to fall to the programmed load pressure, the controller changes the control signal.

The unloader mechanism returns toward the loaded position, allowing the compressor to take in atmospheric air again.

The compressor resumes normal compression and supplies compressed air to the system.

This automatic load/unload cycle is repeated according to compressed-air demand.

Main Functions:

• Controls compressor unloading.
• Regulates inlet airflow during unloading.
• Supports automatic load/unload operation.
• Helps maintain system pressure.
• Reduces unnecessary compression during unloaded operation.
• Helps reduce energy consumption during periods of low air demand.
• Provides reliable pneumatic/mechanical actuation of the unloading system.
• Restores unloader-valve performance during maintenance.

Operating Cycle:

1. Start/Load: The compressor control system commands the compressor to load.
2. Valve Actuation: The unloader mechanism moves to the loading position.
3. Air Intake: Atmospheric air enters the compression element.
4. Compression: The compressor produces compressed air.
5. Pressure Rise: Receiver/system pressure increases.
6. Unload Command: The controller detects the programmed unload condition.
7. Unloader Activation: The unloader valve changes position.
8. Inlet Reduction: Air intake into the compression element is reduced.
9. Unloaded Operation: Compressor output is reduced while system pressure is maintained.
10. Pressure Drop: Compressed-air consumption lowers system pressure.
11. Load Command: The controller requests compressor loading.
12. Unloader Reset: The unloader mechanism returns toward the loaded position.
13. Normal Compression: Air enters the compression element and compressed-air production resumes.

Role of the Unloader Valve:

The unloader valve is a key component in compressor capacity management.

Its primary purpose is to change the compressor from loaded to unloaded operation in response to the control system.

Correct valve movement ensures that the compressor can reduce its air intake when full capacity is not required.

If the valve does not operate correctly, the compressor may remain loaded, fail to load, or cycle incorrectly.

Importance of Correct Sealing:

The unloader assembly relies on properly functioning internal sealing and moving components.

Wear, contamination or deterioration can result in control-air leakage or incorrect valve movement.

A properly serviced unloader valve maintains the required pneumatic response and helps ensure that the compressor transitions smoothly between loaded and unloaded states.

Possible Failure Conditions:

Continuous operation can cause wear, contamination and deterioration of the unloader-valve components.

Potential problems include:

• Valve sticking
• Damaged internal components
• Seal deterioration
• Control-air leakage
• Restricted valve movement
• Delayed valve response
• Incorrect unloading
• Failure to reload
• Continuous loaded operation
• Continuous unloaded operation

Typical compressor symptoms may include:

• Compressor does not unload.
• Compressor does not load correctly.
• Compressor cycles abnormally.
• Excessive energy consumption during low demand.
• System pressure becomes unstable.
• Compressor remains continuously loaded.
• Compressor remains unloaded and fails to produce the required air.
• Abnormal control-air leakage.

If the unloader valve fails to activate during unloading, the compressor may continue compressing air after reaching the required pressure.

If the valve remains in the unloading position, the compressor may fail to deliver the required compressed-air output.

Maintenance Procedure:

Before servicing the unloader valve, stop the compressor, isolate the electrical supply and completely depressurize the compressor according to the applicable Atlas Copco safety procedure.

Inspect the unloader assembly for:

• Valve wear
• Seal deterioration
• Mechanical damage
• Contamination
• Restricted movement
• Control-air leakage
• Incorrect positioning
• Damaged retaining components

Remove the old service components carefully and clean the mating surfaces.

Install the 2906056300 Unloader Valve Kit according to the applicable Atlas Copco service instructions and the compressor-specific parts manual.

Ensure that all components are correctly positioned and securely assembled.

Check the valve for smooth movement before returning the compressor to operation.

After installation, restart the compressor and observe the complete load/unload cycle.

Verify that:

• The compressor loads correctly.
• The compressor unloads at the programmed pressure.
• The unloader valve responds promptly.
• The compressor reloads correctly when system pressure falls.
• System pressure remains stable.
• No abnormal control-air leakage is present.
• No excessive cycling occurs.

A correctly functioning unloader valve allows the compressor to efficiently transition between loaded and unloaded conditions.

The Atlas Copco 2906056300 Unloader Valve Kit is therefore an important service component for maintaining reliable compressor capacity control, stable system pressure and efficient unloaded operation.

Part Number: 2906056300
Alternative Number: 2906-0563-00 / 2906 0563 00
Brand: Atlas Copco
Official Catalog Description: Unloader Valve Kit
Component Type: Unloader valve service/replacement kit
Application: Atlas Copco GA-series oil-injected screw compressors
Referenced Applications: GA90, GA110, GA132, GA160, GA200, GA250 and GA315
Primary Function: Controls compressor unloading
Secondary Function: Regulates inlet airflow during load/unload operation
Operating Function: Changes the compressor between loaded and unloaded conditions according to the control signal
Main Benefits: Reliable unloading, stable system pressure, reduced unnecessary compression, improved capacity control and dependable compressor operation.

Disclaimer: All manufacturer names, trademarks, model numbers, and part numbers are used solely for identification and compatibility purposes. Our products are high-quality aftermarket replacement products and are not manufactured, sponsored, endorsed, or authorized by the original equipment manufacturer (OEM). All trademarks remain the property of their respective owners.